Definition of "centennial"

centennial

/sɛnˈtɛnɪəl/

adjective
not comparable
1. Relating to, or associated with, the commemoration of an event that happened a hundred years before.
2. Happening once in a hundred years.
3. Lasting or aged a hundred years.
  Quotations
  In her grand villa, half-way up the hill, / O'erlooking Florence, but retired and still; / With iron gates, that opened through long lines / Of sacred ilex and centennial pines, […]
  1863 November 23, Henry Wadsworth Longfellow, “The Student’s Tale. The Falcon of Ser Federigo.”, in Tales of a Wayside Inn, Boston, Mass.: Ticknor and Fields, page 34
noun
plural centennials
1. The hundredth anniversary of an event or happening.